Rainbow Mountains in China. Pictures a trip to China in 2014. Amazing area with unique colours in the nature. The formation of Zhangye Danxai Landform dates back to 6 million years ago. The Danxia geological structure was formed by the erosion of red sandstone, forming the isolated peaks and steep outcrops. Its special geological structure, combined with long-term weathering, freeze-thaw peeling, and wind and water erosion gave rise to its present appearance. Photo by Jon Hilmarsson